Save and restore hero tracks

The tracks left by hero were cleared when player saved and
restored the game, or changed levels.  Now the tracks are
saved in the dungeon level, so changing levels keeps the tracks
left by hero in that level.

Also increased the length of tracks from 50 to 100, and
simplify the tracking function.

Thing not done: fade out old tracks when returning to a level.

Breaks saves and bones.

src/allmain.c

@@ -77,6 +77,7 @@ moveloop_preamble(boolean resuming)
         /* give hero initial movement points; new game only--for restore,
            pending movement points were included in the save file */
         u.umovement = NORMAL_SPEED;
+        initrack();
     }
     gc.context.botlx = TRUE; /* for STATUS_HILITES */
     if (resuming) { /* restoring old game */
@@ -89,7 +90,6 @@ moveloop_preamble(boolean resuming)
         gd.defer_see_monsters = FALSE;
         see_monsters();
     }
-    initrack();
 
     u.uz0.dlevel = u.uz.dlevel;
     gc.context.move = 0;